Bad air

At some point I noticed that my office air was getting bad, especially in late afternoon. As this building is somewhat old, and doesn't have good air exchange now that old fireplace isn't used anymore this wasn't very surprising. How bad it was though was a bit more unknown.

I managed to get my hands on a carbon dioxide sensor for some time and was surprised to see co2 levels reaching nearly 2000 ppm during afternoons. No wonder I was getting really tired towards end of days. So I got some improvements made (added intake vents, and wind-powered vacuum at top of old chimney) to improve situation. After this I did notice improvement, but at that time didn't have tools to find out how much the situation really improved.

This was close to a year ago. Out of curiosity I now got a few sensors that should be able to determine this. Specifically, Sensiron SCD30 carbon dioxide sensor and SGX Sensortech MiCS-VZ-89TE air quality sensor.

MiCS measures VOC levels (Volatile Organic Compounds, measured in ppb or parts per billion) by using semiconductor sensor. Datasheet doesn't exactly tell how that is done, but in many similar sensors (as far as I know) this involves hot plate (very tiny one, but nevertheless) on which chemicals and compounds react and change the resistance of this plate which in turn can be measured. This technology isn't very specific, but to put it bluntly, is is still useful to detect many kinds of, well, volatile compounds (most, if not all of which can be considered to be less than healthy to breath in.)  Although datasheet mentions co2, it doesn't really directly measure it and instead gives "co2 equivalent" reading mostly based on VOC reading. Many times these correlate, but not always. But even then, the good side is that these sensors give out a relative reading of air quality and are relatively cheap to be embedded in many consumer-level goods. Think of your phone signalling you that "yeah, you might want to get out of here" when you enter area with less than great air. That at least is target for many of these sensors.

SCD30 on the other hand uses nondispersive infrared sensor (NDIR) to measure actual carbon dioxide level in air, and pretty much nothing else (although I guess some gases/chemicals with similar absorption characteristics as co2 might somewhat affect the reading.)  So this doesn't detect nasty solvents, cigarette smoke or other such things that might be in air. These sensors tend to be a bit more expensive too so they're not that often seen in consumer equipment.

I left these sensors running for some time, below being graph from one day period (noon-ish to noon-ish next day). Sensors actually had been running much longer at this point but I managed to screw up logging (several times, actually) so previous data was lost. Ah well.

Here the co2 level measured by SCD30  is on blue. The level drops when I leave office, eventually falling to current outside air levels (400ppm), and on next day starts to rise immediately when I come in, despite improved air circulation. At least it no longer gets anywhere close to previous 2000ppm levels, instead maxing out at 1200ppm. Not great, but much better than previously.

Red graph shows "equivalent co2" as measured by MiCS. At start of graph it follows SCD30 results relatively closely (not bad!), but veers wildly off at start of next day for some reason. Huge spike you can see in that and VOC reading are because I put small amount of denatured alcohol on tissue and left it near the sensor, to which it reacted immediately. Note that actual (blue) co2 levels weren't changed; only now there was volatile compounds in air that this sensor detected, resulting severe degradation in reported air quality.

I now hope I didn't damage the sensor by leaving alcohol too close to it. Hot plate sensors shouldn't be that sensitive (we're talking about table spoon's worth of alcohol total here) but who knows how this one reacts. Its behavior at end of graph doesn't look too good though. I need to follow its behavior some more to see how it behaves now.

A part of Finnish history

Recently a map where cities of more than 500 people were placed on world map. Terminology aside, I was of course first checking out how Finland looks on this map.

Entire map here

And here is cropped Finland where I very very quickly copy pasted rough current country borders on top of it. Borders are skewed, badly placed and very likely of incorrect size but they are close enough to illustrate my point:

I noticed that for some reason, there is interesting clear divide inside the country, southwestern part of having cities (towns, whatever term you prefer) quite densely, and northeastern part of being very sparse. Hmm. Curious, wonder if there is an historical reason..

Although I was almost certain already, I did quick googling found this article, listing historical borders of Finland. Historically (granted, part of following is my opinion) Finland has been either wild frontier, part of Sweden on west or Novgorod (later Russia) on east, often having been divided up by these two powers. Frontier part being areas, inside or outside these countries allocated borders where their respective governments couldn't or wouldn't reach. Although due to climate, this frontier never was anything like later western frontier of USA, more like wilderness where people could just vanish to live their own life without having to bother with tax collectors, army recruiters and other nuisances of foreign government.

But I digress here. As I remembered, the density border I imagined in above picture matches very closely border agreed by Sweden and Novgorod in 1323, 'Pähkinäsaaren rauha' (as it is known in Finland, Treaty of Nöteborg more internationally). This border stayed in place for next centuries, and changed next time only in 1595 and then 1617.

While I am not familiar on how Sweden and Russia treated this land over this time, I can, based on above map make a guess where Sweden encouraged people moving out and forming communities, while Novgorod .. didn't, and as a result of this one historical border, the entire northeastern part of Finland still remains mostly empty land.

Maybe pointless, but I found this interesting nevertheless.

Car charger (bigger one)

If you are planning on owning an PHEV (plug-in hybrid electric vehicle) or full EV (electric vehicle), you would be absolutely insane to even think of using public charger network, as they're very expensive compared to electricity price you're normally paying. This with some notable exceptions,like Teslas with free supercharger usage.

This is with mainly Finnish focus, but might apply elsewhere too. The electric grid is primarily 3-phase, nominal 230v. Typically normal single-family home receives all three phases, each phase with single "top-level" fuse, typically 25 amps, and within the home all three phases are distributed in a way that this current is not exceeded in any single phase. So for example washing machine and drier, each that can use 16 amps, are placed in different phases.

At home you wouldn't likely be using high-power charger, but instead 2.2 (10-amp) or 3.6kW (16-amp) charger. But there's a problem there: you don't want to overload the main fuses with new high load, so careful planning will be needed.

You can of course switch to larger main fuses (like 3x32A or even higher), but that will increase the electric bill even if you don't use the increased capacity so you don't typically want to go there.

In my case I wanted to install 3.6kW charger, so I had to calculate very carefully how the current wiring in the house goes and what is the expected maximum load of each phase. Fortunately fuse box is very well marked, so it was easy to calculate loads involved in each phase.

As it turned out, stove, sauna and washing/drying machines were the main loads. Phases 2 and 3 were essentially topped out (couldn't use drier when charging the car - not great), but with some care phase 1 could be utilized without too much worry of an overload - especially if charging is timed to happen mostly at nights when other usage is low, so when we got charger installed, I timed car to charge only between 22-07 hours.

Figuring these things out is a bit of an headache, but needs to be done to get things working. And at this point I'm just too fond of electric driving, I wouldn't want to go back to archaic combustion engines.